The invention relates to a thermoanalytical sensor with a substrate that can carry a heat flow between a heat source thermally coupled to the substrate and at least one measurement position formed on the sensor, and further with a thermocouple arrangement formed on a substantially planar surface of the substrate to deliver a thermoelectric signal. Also included in the scope of the invention is a method of producing a sensor of this kind.
Thermoanalytical sensors of this kind are used to measure physical and/or chemical properties of a substance, a substance mixture, and/or a mixture undergoing a reaction, where the measurements are performed as a function of temperature or time and where the sample that is being measured is subjected to a controlled temperature program. Other known examples are the differential heat flow calorimetry and the differential power compensation calorimetry. In both of these applications, the analysis of a sample is performed in relation to a reference sample. The sensors being used in these cases therefore have two measurement positions, i.e., one position to perform the measurements on the sample and the other position to perform the measurements on the reference sample. In the first of the aforesaid applications, the thermoelectric signal delivered by the thermocouple arrangement represents a measure for the difference between the heat flow to the sample and the heat flow to the reference sample. In the second-named application, the thermoelectric signal delivered by the thermocouple arrangement is used to control the respective heat flow rates to the sample and the reference sample in such a manner that the temperature difference between the sample and the reference sample is regulated to zero.
The thermoanalytical sensors can be configured to have the highest possible degree of sensitivity covering, if possible, the entire temperature range of the analysis, i.e., a thermoelectric signal produced as a function of the heat flow is as strong as possible in terms of signal voltage. This can help to obtain a good signal-to-noise ratio. Therefore, as a way to satisfy this, state-of-the-art thermoanalytical sensors (DE 39 16 311 C2 and EP 0 990 893 A1) have a series of thermocouple junctions of the thermocouple arrangement joined in a circuit in such a manner that the thermoelectric signal is produced as the sum of the individual thermocouple voltages. The thermocouple junctions that form the thermocouple arrangement are laid out in a circular pattern around the center of the measurement position (or around the centers of the measurement positions, if there is more than one measurement position) spaced as closely as possible to each other in the azimuthal direction. Consequently, there is no space available that would allow a further increase in the number of thermocouple junctions in these state-of-the-art arrangements.